1-Unsubstituted 3-amino-1H,3H-quinoline-2,4-diones react with nitrourea in dioxane affords novel 3-ureidoquinoline-2,4-diones or imidazo[4,5-c]quinoline-2,4-diones. All products were converted to 2,6-dihydro-imidazo[1,5-c]quinazoline-3,5-diones by refluxing in acetic acid.